Known in the prior art are heavy-duty tubular bodies in which sheathed electric heating elements are located to heat oil flowing from the inlet to the outlet of the body. In order to insure against leakage the inlet and outlet conduits of a body were sealed to the latter by circumferential welds, and like welds were used to seal the disc which closed one end of the body. In order to increase efficiency, several of such bodies were connected in series, but this unduly increased cost because of the extra material involved in such bodies, as well as the requirement of a multiplicity of welds.
My invention provides the advantages of serially-connected circulation heaters, without the increased cost of material and labor. This is accomplished by inserting a baffle member into a tubular body, the baffle member dividing the body into two or more longitudinally-extending chambers, the chambers being isolated from each other except for passages which connect the chambers in serial manner.
When heating oils, for example, it is a known fact that oils have a tendency to carbonize on the sheaths of electric heating elements when the temperature of the oil is approaching degrading temperature and where the flow rate of the oil is low and the watt density of the heating element is high, and such carbonization creates a thermal insulation layer on the sheath to reduce the thermal efficiency of the heating element and cause an early failure thereof.
Heretofore, carbonization was minimized by utilizing electric heating elements of low-watt densities, but this reduced the heating efficienty of the circulation heater. In use of my improved construction the electric heating element may be of relatively high-watt density and carbonization of oils is prevented by increasing the velocity of the oil flowing past the heating elements. Velocity is increased by reducing the cross section of the space through which the oil flows, and I accomplish this by means of a baffle disposed within the tubular body to divide the interior thereof into a plurality of longitudinally-extending chambers each containing one or more sheathed electric heating elements.
The baffle comprises a plurality of vanes radiating from a center section, the vanes having an inherent resiliency in a transverse direction and the longitudinal marginal of the vanes lie in a circle slightly larger than the inner wall surface of the cylindrical body. When the baffle is slid into the body through the open end of the latter, the longitudinal margins of the vanes engage the inner wall surface of the cylindrical body and are flexed transversely and thereby resiliently pressed against the inner wall surface to prevent fluid flow between the chambers past the longitudinal margins of the vanes.
The number of heating elements in each chamber formed by the baffle vanes may be varied to vary the transverse flow space and thus the velocity of the fluid flow. Further, the watt density of the heating elements in certain of the chambers may be varied to suit desired heating requirements.